Certain clockmakers have developed so-called rapid tourbillons, in which only the anchor is located on the cage, the escapement wheel being mounted fixed on the frame of the movement. Such solutions are described in the work entitled “Le Tourbillon” by R. Meis, ISBN No. 2-58917-097-8.
Such devices have been the object of only a few unique pieces. Although the total inertia of the tourbillon is substantially reduced, it is nevertheless significant given that, for construction reasons, it is difficult to image having more than approximately twelve teeth on the fixed escape-wheel. This amounts to saying that, if the balance oscillates at a frequency of 3 Hz, the cage must perform one revolution in four seconds.
Moreover, also know are tourbillon-type devices described, for example, in documents WO 2007/033513, WO 2005/043257, WO 03/017009 and EP 1 564 608. But in these devices, the escape-wheel connected to the anchor is mounted pivotingly on the cage of the tourbillon. These documents therefore cannot be taken into account to resolve the problems which concern devices comprising a fixed escape-wheel.
The present invention aims in particular to realize a tourbillon timepiece comprising a fixed escape-wheel, in which the rotational speed of the cage is reduced.